This invention relates to cooling of electric motors. More specifically, the present invention relates to an apparatus and method to improve the cooling of electric motors by creating a more even airflow over the motor coil windings and stator laminations.
The majority of all commercial and industrial electric fans have an electric motor. These motors generate heat from the motor windings. This heat, when excessive, can degrade overall performance and longevity of the motor. Typically fan designers try to use the xe2x80x9csuctionxe2x80x9d on the rear of the blade and blade hub to help pull the air through the rear of the motor towards the front. This airflow is important in providing cooling for the motor windings, however, there are many structurally necessary elements that are part of the motors which limit the amount of airflow that can help cool the motor.
One of these structurally necessary elements is the motor housing. The motor housing is used to mount the bearings, which support the shaft for rotation. The housing also protects the windings from damage after the motor is assembled, and also acts as an enclosure. The housing has openings, the size of which is mandated by standards organizations such as Underwriters Laboratories. If the openings in the housings exceed a certain mandated size, special cover materials or additional enclosures are required. Motors housings can be cast aluminum, zinc or stamped metal. Motor housings are in contact with the stator, and, in the prior art, closely surround the windings/coils, which leaves little to no area for xe2x80x9cair flowxe2x80x9d through the motor.
A second structural element, which limits airflow through the motor, consists of the stator and rotor. The stator consists of a stack of steel laminations which have copper magnet wire wound on them. Conventionally, the steel is normally sandwiched between the front and the rear housings.
Looking through the rear housing, the wire and stator laminations block the airflow through the motor. The area of opening for air movement through the stator is generally quite small even in relationship to the mandated holes in the motor housings and the motor covers. The prior art housings are so tight against the outside of the laminations that they generally do not allow adequate airflow through the housings and by the coils. The two motor housings typically have a gap where the stator sits, which also allows some of the air entering the rear motor housing to escape, thereby completely bypassing the front coil.
A third structural element, which effects airflow through the motor, is the outside motor cover. For safety purposes most electric motors are surrounded by xe2x80x9cmotor covers.xe2x80x9d Common materials for motor covers are metal and plastic. These covers are usually aesthetic and cover any electrical materials and/or hot motor surfaces. These, motor covers may additionally impede airflow through the motor. Motor covers have vent structures which are usually located at the rear and the front of the motor. Venting provides an airflow path that will enter the xe2x80x9crear motor coverxe2x80x9d and flow mostly around the outside of the motor housing drawing heat from the housings, which in turn draws heat from the stator/windings. This prior art airflow path 30, as illustrated in FIG. 2, has little to no effect on the front coil area of the motor, resulting in uneven heat dissipation throughout the windings. Accordingly, the prior art airflow pattern enters the rear motor cover 11 and travels mainly between the inside of the motor cover walls and the outside of the motor housings 14 and 15. This prior art construction and its resultant airflow does not provide adequate and even cooling of the motor.
The inventive design, set forth in detail below, forces a greater amount of air to be drawn into the motor housing and flow in a path that contacts both the front and rear windings and provides more even cooling of both the front and rear windings and the stator.
In view of the shortcomings of the prior art, the present invention provides a method and apparatus for improved electric motor cooling.
It has now been found that an improved electric motor cooling construction is available wherein the motor housing and covers draw in more air and channel it into an air path that directly contacts the motor stator and coil windings to remove the heat and to more evenly cool the motor.
The improved electric motor comprises a first housing having a first wall defining a first interior space, and at least one opening disposed on a surface of the first housing; a second housing having a second wall defining a second interior space, and at least one opening disposed on a surface of the second housing; and a stator having a plurality of laminations a first portion of windings and a second portion of windings, the plurality of laminations disposed substantially within the first interior space and the second interior space, such that air flows i) into the at least one opening in the first housing, ii) over the first portion of windings, substantially all an exterior portion of the stator laminations, and the second portion of windings, and iii) out the at least one opening in the second housing.
According to another aspect of the invention, a front cover having openings is coupled to the surface of the second housing, and a rear cover having openings is coupled to the front cover and substantially surrounds the first and second housings. The openings in the rear cover are in fluid communication with the openings in first housing, and the openings in the front cover are adjacent and in fluid communication with the openings in the second housing.
According to a further aspect of the invention, the stator is substantially square.
According to yet a further aspect of the invention, the at least one opening in the first housing is a first plurality of openings and the at least one opening in the second housing is a second plurality of openings, at least a portion of the first plurality of openings and at least a portion of the second plurality of openings in respective planes substantially parallel to one another.
According to another aspect of the invention, the motor housings are in contact with the stator and have airflow channels therebetween.
According to yet another aspect of the invention, the stator is substantially round.
According to still another aspect of the invention, the front motor cover contacts the front motor housing to seal off airflow, forcing air through the motor.
According to yet a further aspect of the invention, the front and rear motor housings have a reduced gap therebetween so that airflow is inhibited from escaping from between the motor housings.
According to another aspect of the invention, the electric motor has a reduced operating temperature and a more even cooling of the stator windings and laminations.
These and other aspects of the invention are set forth below with reference to the drawings and the description of exemplary embodiments of the invention.